1. Field of the Invention
The present invention relates to an improved manifold heat exchanger for an internal combustion engine.
2. Description of the Prior Art
Internal combustion engines have heretofore included manifold heat exchangers for transferring heat from exhaust gases flowing through an exhaust manifold to a combustible charge flowing through an intake manifold. Heating of the charge to combustion enhances the initial engine performance during cold weather.
U.S. Pat. Nos. 2,108,639, 2,651,507 and 2,725,862 disclose manifold heat exchangers for internal combustion engines wherein temperature responsive valves control the heat transfer between the exhaust and intake manifolds. These valves have been necessary with prior art manifold heat exchangers in order to terminate the heating of the combustible charge once steady state operating temperatures have been reached. Otherwise, the exhaust gases would transfer too much heat to the combustible charge within the intake manifold during steady state operation with these prior art manifold heat exchangers.
Also U.S. Pat. Nos. 2,251,630, 2,252,972 and 2,936,746 disclose other intake manifold heaters. The manifold heater of the U.S. Pat. No. 2,251,630 incorporates an electric heating element disposed within the intake manifold to warm the combustible charge. The manifold heater of the U.S. Pat. No. 2,252,972 passes air through a closed conduit within the exhaust manifold and then feeds this air to the intake manifold downstream from a carburetor that feeds the intake manifold. The manifold heater of the U.S. Pat. No. 2,936,746 utilizes the engine coolant to heat the intake manifold. This coolant is present in a liquid state as it performs its heat exchange function during engine operation.